GM and non-GM coexistence, as defined by the European commission, defines a product as non-GM if it contains less than 0.9% of GM material. A good solution to avoid the risk of mixing GM and non-GM in the landscape and during collection process is to define homogeneous production zone for GM and non GM. To allow such zone to be defined cooperation between grain merchants is needed. In this paper we want to evaluate if such cooperation have an interest for grain collection management. To do so we used a simulation model of the collection process. The simulation shows that such cooperation between companies allows them to collect more non GM product than the situation where they operate separately.